Recent origin of a chiasmatic sex trivalent in Australian Pseudotetracha tiger beetles

Abstract

Meiotic behavior based on observations of the first and second divisions was studied in males of four taxa of the Australian tiger beetle genus Pseudotetracha of the tribe Megacephalini (Coleoptera). Pseudotetracha blackburni clade 1 shows 10 pairs of autosomes plus a trivalent that is hypothesized to be the result of either a translocation or a fusion in which the original heterosomes (very likely XY) and an autosomal pair are involved, giving rise to a recently established neo‐X1X2Y sex chromosome system of chiasmatic nature. The origin of this karyotype has been determined to have taken place 2.30–3.72 million years in the past using a molecular clock based on the 16S rRNA substitution rate. Pseudotetracha blackburni clade 2 shows a meioformula of the type n = 11 + XY, the same as that found in the related taxon P. australis. Previous data for P. whelani, with 12 pairs of autosomes and an XY sex chromosome system, are confirmed in this survey. The multiple chiasmatic sex chromosome system of P. blackburni clade 1 is considered to be of recent origin and with an evolutionarily short‐life confined to this species, where close relatives exhibit simple genetic systems, in contrast to the long evolutionary life of the multiple achiasmatic sex chromosome system broadly found in the tribes Cicindelini and Collyrini. The implications of this chromosomal rearrangement in terms of recombination and speciation are discussed. The results of this work, together with the available cytogenetic data for other Megacephalini species, are interpreted in the light of recent molecular phylogenies of the tribe, showing evidence of a possible process of karyotypic orthoselection with recurrent cycles of incorporation of autosomes to the heterosome pair and subsequent loss of the Y chromosome in Tetracha and Pseudotetracha.

Molecular phylogeny and divergence time estimation of Cosmodela (Coleoptera: Carabidae: Cicindelinae) tiger beetle species from Southeast Asia

“…), including tiger beetles (López‐López et al . , ). The nuclear fragment wingless (Wild & Maddison ) has also been successfully used for determining the phylogeny of several groups of beetles (Sota & Vogler ; Ober & Maddison ).…”

Evolution and diversification of the Southern Chilean genus Ceroglossus (Coleoptera, Carabidae) during the Pleistocene glaciations

“…Additionally, a further rearrangement in C. chilensis resulted in the creation of a trivalent, corresponding to a multiple sex chromosome system similar to that observed in other Carabidae (Serrano, 1980) or Cicindelidae (López‐López et al ., 2013). This rearrangement involved an autosome and a heterosome (Fig.…”

“…This leads to the subsequent isolation of the respective variants, which finally results in their separation as independent species. This process has been shown to be important for the diversification of different groups of organisms (Kawakami et al ., 2011; de Vos et al ., 2020), including beetles (Gómez‐Zurita et al ., 2004; López‐López et al ., 2013; Xavier et al ., 2018).…”

Comparative cytogenetic analysis of marine Palaemon species reveals a X1X1X2X2/X1X2Y sex chromosome system in Palaemon elegans

“…In regard to the multiple sex chromosome systems, the initial stage of differentiation seems to be associated with chromosomal rearrangements between the chromosomes bearing sex-determining genes and an autosome (e.g. [48–50]). Consequently, due to rearrangements, even newly evolved sex chromosomes can be heteromorphic [51] and not necessarily involve heterochromatin increase [49].…”